Electrostatic precipitator construction having ladder bar spacers

ABSTRACT

The present invention relates to an improved construction for an electrostatic precipitator having ladder bar spacers. The electrostatic precipitator collects solid particles carried by a flue gas from a source of combustion. The precipitator includes a plurality of spaced plates for collecting solid particles from the flue gas by electrostatic attraction of the solid particles to the plates. A second plurality of elongated electrodes is positioned among the plates. Each of the electrodes is mounted between a pair of adjacent plates. Each of the electrodes is parallel to the other electrodes and is parallel to the plates. A third plurality of ladder bars is positioned between adjacent plates to hold the plates in a flat attitude and to maintain adjacent surfaces of adjacent plates substantially equidistantly spaced from one another. Each of the ladder bars has a connector bar secured to one of the pair of adjacent surfaces. Each of the ladder bars has a fourth plurality of holder bars. Each of the holder bars having one end connected to its respective connector bar and extending outwardly from the connector bar toward the other of the pair of adjacent surfaces. A contact on the other end of each holder bar engages the other of the pair of adjacent surfaces to hold the pair of adjacent surfaces apart.

BACKGROUND OF THE INVENTION

A commonly accepted practice of removing solid particles from a flue gasincludes the utilization of an electrostatic precipitator to hold thesolid particles without inhibiting the flow of the flue gas. Typically,an electrostatic precipitator is positioned in the flue between theoutlet of a boiler and a smokestack.

The ordinary construction of an electrostatic precipitator includes aplurality of large, flat, metal plates which are spaced from each other.The metal plates may have a height of up to 30 feet or more, and a widthof up to 10 feet or more. It is to be appreciated that the specific sizeof the plates in a given precipitator is dependant upon the particularprecipitator construction for a given application. Ideally, the flatplates are equidistantly spaced from each other. A second plurality ofelongated electrodes is positioned among the plates. The electrodes arepositioned between each pair of adjacent plates. The elongatedelectrodes are equidistantly spaced from adjacent plates.

The uniform spacing of the elongated electrodes from the plates isnecessary to have a uniform electrostatic charge between the elongatedelectrodes and the plates. A uniform electrostatic charge generatesuniform collection of solid particles on the plates. Typically, thesolid particles are removed from the plates by rapping the plates tovibrate the plates and, thereby, cause the collected solid particles todrop off of the plates in clusters into collectors under the plates.

The flue gas which enters the electrostatic precipitator is hot.Commonly, additional heat enters the precipitator in the form of firescaused by problems in the operation of the boiler. The continualexposure of the plates to heat causes the plates to warp or buckle. Thewarping or buckling of the plates destroys the uniform spacing betweenadjacent surfaces of adjacent plates and uniform spacing between each ofthe elongated electrodes and the respective adjacent plates. Thereby,the effectiveness of the precipitator in removing solid particles from aflue gas is reduced so that the precipitator has a lower capacity.Consequently, the capacity of the boiler, which produces the flue gas,must also be lowered to comply with emissions regulations. In the caseof a power generation unit, as the capacity of the boiler is reduced,the capacity of a power generating system connected to the boiler isalso reduced. In order to maintain an electrostatic precipitator fullyeffective, it is desirable to maintain the spaced plates of theprecipitator in an equidistantly spaced relationship to each other andto the electrodes.

One apparatus for holding electrostatic precipitator plates in anequidistantly spaced relationship is taught in U.S. Pat. No. 4,007,023,issued Feb. 8, 1977, to Batza et el, entitled "ElectrostaticPrecipitator With Collector-electrode Spacers." The Batza et el patentdiscloses spacer construction for use between adjacent collectingelectrode strips to hold the strips apart an equal distance from eachother. Each spacer includes a bracket which is fixed to one of thestrips. A spacer body is connected to the bracket by a pivot. A secondbracket is fixed to a second electrode strip. The spacer body includes aslot for receiving the second bracket. The Batza et el device isexpensive to manufacture and difficult to install, since the twobrackets must be perfectly aligned on facing surfaces. Furthermore, theBatza spacer provides many sharp edges which create localizedelectrostatic charges to distort the electrostatic field around thestrips thereby reducing tne effectiveness of the electrostaticprecipitator. Another known spacer is one which has an "H" barconstruction. This spacer has several disadvantages in that the spaceris made up of three seperate pieces which are welded together. Inparticular, it has been found that there is sufficient variation in sizeof the spacers to create a misalignment of the plates. The variation insize cannot be adapted in the field. Furthermore, each spacer must bemounted on its respective surface individually.

SUMMARY OF THE INVENTION

The subject matter of this invention is an electrostatic precipitatorfor collecting solid particles carried by a flue gas from a source ofcombustion. The precipitator includes a plurality of spaced parallelplates for collecting solid particles by electrostatic attraction of thesolid particles to the plates. A second plurality of elongatedelectrodes is mounted between adjacent plates. Each of the elongatedelectrodes is parallel to the other electrodes and to the plates. Theelongated electrodes are equidistantly spaced between the plates. Athird plurality of ladder bars is positioned between adjacent plates tohold the plates in a flat attitude and to maintain adjacent surfaces ofthe plates equidistantly spaced from one another. Each of the ladderbars has a connector bar secured to a pair of adjacent surfaces. Afourth plurality of holder bars is connected to each connector bar atone end of each of the holder bars. The holder bars extend outward andaway from the connector bar toward the other of the pair of adjacentsurfaces. A contact is connected to the other end of each holder barabutting the other of the pair of adjacent surfaces to hold the pair ofadjacent surfaces in a spaced relationship.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an electrostatic precipitator embodyingthe herein described invention positioned between a boiler and asmokestack.

FIG. 2 is an enlarged fragmentary broken-away perspective view of theelectrostatic precipitator shown in FIG. 1 showing a plurality of spacedplates and ladder bars attached to certain of the plates to maintain theplates in a uniform spaced relationship;

FIG. 3 is a plan view of a portion of the precipitator of FIG. 2 takenon line 3--3 of FIG. 2 showing the relative positioning of plates andelongated electrodes with ladder bars between adjacent plates;

FIG. 4 is a fragmentary enlarged perspective view of a plurality ofplates of the electrostatic precipitator of FIG. 2 showing ladder barsmounted between adjacent plates;

FIG. 5 is a side elevational view of a plurality of plates showing thepositioning of the ladder bars on the plates;

FIG. 6 is an enlarged cross sectional view taken on line 6--6 of FIG. 5;

FIG. 7 is a side elevational view of a multiple holder bar ladder bar;

FIG. 8 is a side elevational view of a double "U" ladder bar:

FIG. 9 is a side elevational view of a ladder bar having a plurality ofholder bars;

FIG. 10 is a side elevational view of a double "Z" ladder bar;

FIG. 11 is a triple "U" ladder bar; and

FIG. 12 is a side elevational view of a ladder bar having triple holderbars.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and especially to FIG. 1, an electrostaticprecipitator embodying the herein disclosed invention is generallyindicated by numeral 10. The precipitator is mounted in a flue between aconventional boiler 12 and a conventional smokestack 14. Looking now toFIG. 2, it may be seen that the precipitator includes a housing 16 witha plurality of identical spaced flat metal plates 18 mounted in thehousing. A second plurality of elongated electrodes 20 is positionedbetween the plates. A third plurality of ladder bars 22, is mounted onplates 18 to maintain the plates in a uniform spaced relationship and toflatten those plates which are warped or buckled.

Electrodes 20 and plates 18 are connected to a conventional source of anelectrostatic charge which is not shown herein. As is well known in theart, the source of the electrostatic charge creates an electrostaticcharge on the electrodes and an opposite electrostatic charge on theplates so that solid particles carried by the flue gas are attracted toplates 18. As is conventional, the cleansed flue gas then flows tosmokestack 14.

The construction of the electrostatic precipitator is conventional inthat the electrostatic precipitator housing 16 has its inlet connectedto boiler 12. The housing is enclosed and has its outlet connected tosmokestack 14. The bottom of housing 16 includes a plurality ofcollector hoppers 24, which are adapted to receive the solid particleswhich are collected on the plates. The hoppers are opened at theirrespective bottoms to discharge the collected solid particles from thehousing. Housing 16 includes a plurality of legs 26 to support theprecipitator.

A high tension frame 28 is mounted in housing 16. The frame 28 isconventional in its construction and is connected to the source ofelectrostatic charge. The elongated electrodes 20 are mounted on frame28. Each of the electrodes 20 is a single metallic electricallyconductive wire 30 with a weight 32 secured to the end of the wire tohold the wire taut and perfectly perpendicular to the horizontal. Sinceeach of the electrodes 20 is taut by its respective weight, all of theelectrodes are parallel to each other. A lower high tension frame (notshown) restrains the wire weights in place to prevent movement. Thisframe is conventoinal in its design.

The precipitator includes a plurality of plate support rails 34 commonlyknown as anvil beams, mounted within housing 16. Plates 18 are mountedbetween adjacent rails 34. Each plate 18 includes a metallicelectronically conductive collector surface 36 with a plurality ofstiffeners 38 formed in the plate to make the plate rigid. A pair ofears 40 is fixed to the upper portion of each of the collector surfacesto provide a means for supporting the respective plate on rails 34. Aplurality of side spacer bars 42 is secured to the ends of the plates tohold the plates in a selected spaced relationship relative to eachother.

As my be seen in FIG. 3, the plates are regularly spaced from each otherand a plurality of electrodes is positioned between a pair of adjacentplates. The electrodes are equidistantly spaced between the plates.

In a new installation, the plates and electrodes are equidistantly andregularly spaced as shown in FIG. 3. However, after a prolonged usage ofthe precipitator, the plates tend to warp and buckle. The resultingdisperity in the distance between adjacent plates and electrodes reducesthe effectiveness of the precipitator. In order to bring theprecipitator back to its original effectiveness and in some instancesprovide an improved capacity, ladder bars 22 are positioned betweenadjacent surfaces of adjacent plates to straighten the plates and toequalize the distance between adjacent surfaces of adjacent plates.

Referring now to FIG. 12, ladder bar 22 is shown therein. Ladder bar 22includes an elongated connector bar 44 which has a circular crosssection. The ends of the connector bar are rounded. Three holder bars46, 48 and 50 are fixed to the connector bar 44. Holder bars 46 and 50are positioned adjacent to the ends of the connector bar. Holder bar 48is positioned midway between holder bars 46 and 50. Each of the holderbars 46, 48, and 50, has one end welded to connector bar 44. Holder bars46, 48, and 50, are each perpendicular to the connector bar and areparallel to each other. Each of the holder bars 46, 48, and 50, is ametallic bar having a circular cross section. Contacts or terminalportions 52, 54, and 56 are fixed to the other end of each of the holderbars 46, 48, and 50, respectively. Each of the contacts is welded to itsrespective holder bar. Contacts 52, 54, and 56 are perpendicular to therespective holder bars, and the contacts are in line. The contacts areparallel to the connector bar. Each of the contacts or terminal portionsis a metallic bar having a circular cross section. Each end of eachcontact is rounded so that all of the ends of the ladder bar 22 arerounded.

As may be seen in FIG. 5, each of the ladder bars is fixed to onesurface of a pair of opposed parallel surfaces of a pair of plates. Eachladder bar has its connector bar welded to a plate in an attitudewherein the holder bars are perpendicular to the respective plate. Whenall of the required ladder bars are mounted on a given surface of aplate, the adjacent plate is then placed into the engagement with thecontacts of the ladder bars. In the event that the adjacent plate iswarped so that the plate bows toward the ladder bars, the weight of theplate creates a moment which applies a force against the ladder bars tostraighten the plate. Once the adjacent plate is positioned, additionalladder bars are mounted on the other side of that adjacent plate. Theadditional plates have ladder bars spaced in line with the other ladderbars as shown in FIGS. 3, 4, and 5. The positioning of the ladder barsin line means that the forces are applied to the plates at thestiffiners where the ladder bars are secured to the respective plates.

Positioning of a plurality of ladder bars on one plate provides a meansfor holding an adjacent plate at a selected distance from the one plateeven if one or both of the plates are warped or buckled. The weight ofthe plates causes the plates to be straightened, but the ladder barshold adjacent plates apart a set distance. The present construction hasone end of each holder bar secured to a plate, but the other end is freeto move relative to the abutting plate. The plates are substantiallystraightened when all of the plates are interconnected between ladderbars abutting the adjacent plates of each pair of adjacent plates.

In the event that the length of the ladder bar 22, with three holderbars, is too long for one of the plates, it is readily apparent that theconnector bar may be cut off adjacent to intermediate holder bar 48 andonly two holder bars are used. Such an application is shown in FIGS. 2and 5 to demonstrate that the ladder bar may be easily adapted for anyapplication. It is to be appreciated that all of these repairs are doneon site, that is, at the location of the precipitator. Due to errors ininventory or planning, the proper size ladder bars may not be readilyavailable thus, the longer ladder bars may be cut to size at a givenapplication.

Looking now to FIG. 7, a double "U" spaced ladder bar 100 is showntherein. Ladder bar 100 includes a noncontinuous connector bar which hastwo portions 102 and 104. A holder bar 106 is formed integral with oneend of portion 102 of the connector bar. A holder bar 108 is formedintegral with the other end of portion 102. A third holder bar 110 isformed integral with one end of portion 104, and a holder bar 112 isformed integral with the other end of portion 104. An intermediatecontact 114 is formed integral with the ends of holder bars 108 and 110connecting holder bars 108 and 110. An end contact 116 is formedintegral with one end of holder bar 106, and the contact extends inwardtoward contact 114. A second end contact 118 is formed integral withholder bar 112 and extends inward toward contact 114. Holder bars 106and 108 are perpendicular to portion 102. Holder bars 110 and 112 areperpendicular to portion 104. The holder bars 106, 108, 110, and 112 areall parallel to each other. Contacts 114, 116, and 118 are in line andare parallel to portions 102 and 104. The entire ladder bar 110 is aunitary metallic rod having a circular cross section. The ladder bar isformed of a single metal rod. The ends of the rod which form the ends ofcontacts 116 and 118 are rounded portions. Ladder bar 100 is utilized inthe same manner as ladder bar 22, in that portions 102 and 104 of theconnector bar are welded to a surface of a plate with holder bars 106,108, 110, and 112 perpendicular to that surface.

Referring now to FIG. 8, a double "U" shaped ladder bar 200 is showntherein. Ladder bar 200 includes a elongated straight connector bar 202which has a holder bar 204 formed integral with one end, and a holderbar 206 formed integral with the other end. The holder bars 204 and 206are each perpendicular to connector bar 202 and are parallel to eachother. A contact 208 is formed integral with holder bar 204, and acontact 210 is formed integral with holder bar 206. Contacts 208 and 210are perpendicular to holder bars 204 and 206, respectively. Contacts 208and 210 are in line. Each of the contacts has a rounded end portion.From the foregoing, it may be seen that the ladder bar 200 may bereadily formed from a single metallic rod having a circular crosssection. The bar is simply bent to shape.

Referring now to FIG. 9, ladder bar 300 is shown therein. Ladder bar 300includes an intermittent connector bar, which includes a pair ofinternal portions 302 and 304 which are in line with each other. Aspaced end portion 306 is in line with portion 302 as is a spaced endportion 308. A holder bar 310 has one end formed integral with one endof portion 306. Another holder bar 312 has one end formed integral withone end of portion 302, while another holder bar 314 has one end formedintegral with the other end of portion 302. A holder bar 316 has one endformed integral with portion 304 and another holder bar 318 is formedintegral with the other end of portion 304. A holder bar 320 has one endformed integral with portion 308. A contact 322 has one end formedintegral with holder bar 310 and the other end formed integral with anend of holder bar 312. A contact 324 has one end formed integral withthe other end of holder bar 314, and the other end of the contact isformed integral with holder bar 316. A contact 326 has one end formedintegral with holder bar 318 and the other end formed integral withholder bar 320. Contacts 322, 324, and 326 are in line and are parallelto the connector bar.

Ladder bar 300 is formed of a single metallic bar having a uniformcircular cross section. The bar is bent to form the appropriate portionsof the ladder bar. The ends of the bar which are the ends of portion 306and 308 are rounded. Ladder bar 300 is used in the same manner as ladderbar 22. Portions of the connector bar are welded to a plate with theplane of the ladder bar being perpendicular to the plate.

Referring now to FIG. 10, a double "Z" ladder bar 400 is shown therein.Ladder bar 400 includes an elongated straight connector bar 402. Aholder bar 404 is formed integral with one end of connector bar 402, anda holder bar 406 is formed integral with the other end of connector bar402. A contact 408 is formed integral with holder bar 404, and a contact410 is formed integral with holder bar 406. Contacts 408 and 410 are inline and are parallel to connector bar 402. The ends of contacts 408 and410 are rounded. Ladder bar 400 is formed of a single uniform piece ofmetallic rod which is bent to a selected shape to form the ladder bar.Ladder bar 400 is used in the same manner as is ladder bar 22.

Referring now to FIG. 11, ladder bar 500 is shown therein. Ladder bar500 includes a straight elongated connector bar 502. A holder bar 504 isformed integral with one end of the connector bar, and a holder bar 506is formed integral with the other end of the connector bar. A metallicholder bar 508 is fixed to the connector bar 502 midway betweenconnector bars 504 and 506. Holder bars 504, 506 and 508 areperpendicular to the connector bar and are parallel to each other. Acontact 510 is formed integral with holder bar 504. A contact 512 isformed integral with holder bar 508. A contact 514 is formed integralwith holder bar 506. Contacts 510, 512, and 514 are in line and areparallel to connector bar 504. The ends of the contacts 510, 512, and514 are rounded.

Ladder bar 500 is formed by bending a single unitary metallic rod havinga uniform circular cross section to form the connector bars 504 and 506and the respective contacts. A second piece of metallic rod is bent to ashape to form a holder bar 508 with contact 512, and the holder bar iswelded to connector rod 502 to complete the ladder rod. Ladder rod 500is used in the same manner is as ladder bar 22.

Each of the ladder bars 22, 100, 200, 300, 400, and 500 has a connectorbar which is attached to the surface of a plate and welded. The ladderbar is positioned on the plate adjacent to and in line with thestiffener on the plate. The plane of each ladder bar is substantiallyperpendicular to the surface of the plate. The distance between thecontacts and the connector bar is substantially equal to the distancebetween adjacent surfaces of adjacent plates. Since the connector bar iswelded to one of the adjacent plates, the contacts abut the adjacentsurface of the adjacent plate. As was mentioned above, the plates arefixed into a flattened attitude making the distance between adjacentsurfaces uniform. It follows that the equidistantly spaced portions ofthe elongated electrodes then provide a uniformed positioning relativeto the plates. As flue gas flows between the plates and becomes chargedby engagement with the electrodes, the solid particles are depositedupon the plates.

The instant invention is described in detail herein and is shown in theaccompanying drawings. It is readily apparent that those skilled in theart may make various modifications and changes without departing fromthe spirit and scope of the herein disclosed invention. It is to beexpressly understood that the instant invention is limited only by theappended claims.

What is claimed is:
 1. In an electrostatic precipitator for collectingsolid particles carried by a flue gas from a source of combustion, saidprecipitator including a plurality of parallel precipitator platesspaced from and adjacent one another for collecting solid particles byelectrostatic attraction of solid particles to the plates, and a secondplurality of elongated electrodes mounted between adjacent platessubstantially parallel to each other and substantially parallel to theplates, each of said elongated electrodes being substantiallyequidistantly spaced from adjacent electrodes, the improvementcomprising: a third plurality of ladder bars positioned between adjacentplates to hold adjacent surfaces of adjacent plates in an equidistantlyspaced relationship, each of said ladder bars having a connector barsecured to one of a pair of the adjacent surfaces, .[.each of saidconnector bars having a circular cross section,.]. and each of saidladder bars having a fourth plurality of holder bars, .[.each of saidholder bars having a circular cross section,.]. each of the holder barshaving one end connected to its respective connector bar and extendingoutward from the connector bar toward the other of the pair of adjacentsurfaces.
 2. In an electrostatic precipitator for collecting solidparticles carried by a flue gas from a source of combustion as definedin claim 1; wherein each ladder bar is a formed unitary metal rod.
 3. Inan electrostatic precipitator for collecting solid particles carried bya flue gas from a source of combustion as defined in claim 1; whereineach ladder bar is a metal rod having a circular cross section.
 4. In anelectrostatic precipitator for collecting solid particles carried by aflue gas from a source of combustion as defined in claim 1; wherein eachholder bar has a terminal portion on .[.the end opposite said one end.]..Iadd.its outward extension.Iaddend., each of said terminal portionshaving a circular cross section.
 5. In an electrostatic precipitator forcollecting solid particles carried by a flue gas from a source ofcombustion as defined in claim 1; including a contact on the .[.otherend.]. .Iadd.outward extension .Iaddend.of each holder bar engageablewith the other of the pair of adjacent surfaces.
 6. In an electrostaticprecipitator for collecting solid particles carried by a flue gas from asource of combustion as defined in claim 5; wherein each contact isformed integral with its respective holder bar.
 7. In an elecrostaticprecipitator for collecting solid particles carried by a flue gas from asource of combustion as defined in claim 5; wherein each contact issubstantially parallel to its respective connector bar.
 8. In anelectrostatic precipitator for collecting solid particles carried by aflue gas from a source of combustion as defined in claim 1; wherein eachholder bar is substantially perpendicular to its respective connectorbar.